User Tools

Site Tools


checking_20if_20a_20library_20is_20installed

Checking if a library is INSTALLed

by Jon Ripley, January 2006

BBC BASIC for Windows provides no built in function to check whether a library has been loaded into memory using the INSTALL command.

The following routine FN_IsInstalled(lib$) implements a method to check if a library is currently INSTALLed:

        DEF FN_IsInstalled(lib$)
        IF ?HIMEM = 0 THEN = FALSE
        LOCAL P%, tmp$
        SYS "CharUpperBuff", !^lib$, LEN lib$
        IF RIGHT$(lib$,4) = ".BBC" THEN lib$ = LEFT$(lib$, LEN lib$ - 4)
        P% = HIMEM
        REPEAT
          tmp$ = $$(P%+4)
          IF lib$ = "-" THEN PRINT tmp$
          SYS "CharUpperBuff", !^tmp$, LEN tmp$
          IF lib$ = tmp$ OR tmp$ = lib$ + ".BBC" THEN = TRUE
          P% += ?P%
          WHILE ?P% AND ?P% < &FF
            P% += ?P%
          ENDWHILE
        UNTIL (!P% AND &FFFFFF) = &FFFF00
        = FALSE 


To check if a library is installed use code similar to the following:

        IF FN_IsInstalled(@lib$+"WINLIB") THEN
          PRINT "WINLIB is installed."
        ELSE
          PRINT "WINLIB is not installed."
        ENDIF 


To list all installed libraries call FN_IsInstalled(“-”).

Installing a library only once


When you INSTALL a library, BBC BASIC for Windows checks whether that library is already installed (version 5.91a or later only), however it performs a case-sensitive comparison of the supplied path/filename. It will reliably detect the same INSTALL statement being executed a second time, but not necessarily a different INSTALL statement which installs the same library but specifies it differently.

Installing a library more than once is safe but wastes memory. If this is a concern, the following routine can be used instead of INSTALL:

        DEF PROC_InstallOnce(lib$)
        IF NOT FN_IsInstalled(lib$) THEN INSTALL lib$
        ENDPROC 
This website uses cookies. By using the website, you agree with storing cookies on your computer. Also you acknowledge that you have read and understand our Privacy Policy. If you do not agree leave the website.More information about cookies
checking_20if_20a_20library_20is_20installed.txt · Last modified: 2018/04/15 19:11 by tbest3112